Coal dust present in coal mines generally found as is suspended in air, can be easily disturbed by mining and extraction operations. Once disturbed, a danger exists due to poor ventilation in coal mines and if an explosion were to occur, the suspended coal dust could act as a catalyst and as a conduit for fire resulting from the explosion, and allowing for the fire to spread more easily though the mine shafts. The suspended dust is deposited onto areas of the mine, such as the mine roof, the mine floors, and sidewalls of the mine known as ribs.
Rock dust has been utilized in the coal mining industry as a means to limit explosions these explosions in mines. Rock dust is typically an off-white solid, which is reflective against the black coal and renders the workable, coated area lighter than surrounding areas. Rock dust at a plus 80% non-combustible level provides a suitable material to be placed onto the mine roof, ribs, and floor. Rock dust is also required to meet certain requirements in the United States as set forth by 30 CFR §75.2 regulations that govern underground mining. For example, rock dust may be limestone rock dust.
Known dry rock dust application processes include, for example, application of particles such as calcium carbonate powder as rock dust. The calcium carbonate when exposed to heat from a flame is broken down into carbon dioxide, quenching the flame as described in U.S. Patent App. Publ. No. 2012/0111583 to Brown et al., entitled “Stone Dusting,” published May 10, 2012, which is incorporated by reference herein. Known dry dusting processes, however, include a major limitation of interrupting production to apply the rock dust particles in mines. Known application processes of applying dry rock dust use a means of slinging or blowing rock dust onto surfaces in a manner that leads to quantities of dust escaping to contaminate downstream airways. Thus, mining paths are evacuated prior to a rock dust application to prevent contamination of downstream personnel and to prevent them from being affected by the dusting out of the mine. “Dusting out” is a term generally used by miners to describe such an event that occurs during the application of dry rock dust where the rock dust enters the air stream to a degrees that makes visibility poor and may cause breathing issues that are potential originators of diseases such as silicoses.
Wet rock dust application processes are known and eliminate the problem of contamination of downstream airways. To wet dust a mine, dry rock dust particles are mixed with a liquid such as water and released as a slurry onto mine surfaces. Under 30 CFR 75.2(d), however, wet rock-dusting of ribs and a mine roof does not elimination the need to dry rock-dust a mine floor. Further, when the slurry formed by wet rock dust dries out, the dried out slurry formed a hardened cake layer on a treated mine surface that is not as easily dispersed from the treated surfaces. Formation of such a hardened cake layer is referable to as caking, which is a term used by the Mine Safety and Health Administration (“MSHA”) to explain the moisture content of rock dust that has been applied to an area that is at a level such that the rock dust is not effectively dispersible as the rock dust particles are bonded or caked together. Thus, dangerous dust deposits may escape from and through the caked rock dust during an event, such as an explosion, and not be protected by the rock dust as intended.
The present disclosure describes a dry dusting application utilizing aerated rock dust to provide a dispersible coating on mine surfaces that does not disrupt production when applied.
The drawings are not intended to be limiting in any way, and it is contemplated that various embodiments of the invention may be carried out in a variety of other ways, including those not necessarily depicted in the drawings. The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention; it being understood, however, that this invention is not limited to the precise arrangements shown.